Non-invasive imaging and analysis of targets is a valuable technique for acquiring information about systems or targets without undesirable side effects, such as damaging the target or system being analyzed. In the case of analyzing living entities, such as human tissue, undesirable side effects of invasive analysis include the risk of infection along with pain and discomfort associated with the invasive process. In the case of quality control, it enables non-destructive imaging and analysis on a routine basis.
Optical coherence tomography (OCT) is a technology for non-invasive imaging and analysis. There are more than one OCT techniques. Time Domain OCT (TD-OCT) typically uses a broadband optical source with a short coherence length, such as a super-luminescent diode (SLD), to probe and analyze or image a target. Multiple Reference OCT (MRO) is a version of TD-OCT that uses multiple reference signals. Another OCT technique is Fourier Domain OCT (FD-OCT).
A version of Fourier Domain OCT, called Swept Source OCT (SS-OCT), typically uses a narrow band laser optical source whose frequency (or wavelength) is swept (or varied) over a broad wavelength range. In TD-OCT systems the bandwidth of the broadband optical source determines the depth resolution. In SS-OCT systems the wavelength range over which the optical source is swept determines the depth resolution.
Another version of Fourier Domain OCT, often referred to as Spectral Domain OCT (SD-OCT), typically uses a broad band optical source and a spectrometer to separate out wavelengths and detect signals at different wavelengths by means of a multi-segment detector.
OCT depth scans can provide useful sub-surface information including, but not limited to: sub-surface images of regions of tissue; measurement of thickness of layers of tissue; magnitude of regions of abnormal tissue growth; measurement of concentration of metabolites, such as glucose, in tissue fluids; measurement of concentration of metabolites, such as glucose, in blood. More generally OCT depth scans can provide useful sub-surface information regarding attributes of tissue.
It is often useful to acquire OCT sub-surface scans of tissue at known locations with respect to the tissue surface. While OCT can produce two dimensional images of the surface of a target such as tissue, there are conventional imaging technologies that can capture surface images, such as a camera employing a conventional charged coupled device (CCD). Such conventional imaging devices can readily capture images of the surface of tissue.
Tissue can be imaged to acquire a surface fingerprint by various techniques including, but not limited to: cameras using one or more conventional charged coupled device (CCD); an array of conducting sensors in conjunction with an RF generator (as in an iPhone fingerprint detector); ultrasonic imaging systems, such as those using capacitive micro-machined ultrasound transducers (CMUTs).
While fingerprint sensors, such as an array of conducting sensors in conjunction with an RF generator, are used to ensure use by authorized individuals, such sensors are vulnerable to being hacked, for example, by artificial (stick on) fingerprints. There is therefore an unmet need for a more secure authorization technique. Moreover, while secure methods exist, they are not sufficiently fast for many consumer applications, where the expectation is for rapid validation of identity.
Systems and method needs to be both secure and rapid to be useful. What is needed is a system and method for secure validation of fingerprints that is both rapid and capable of determining blood flow or monitoring other bio-signs as a sign of life.